1. Field of the Invention
The present invention relates to a system which restrains components to prevent relative movement, and then releases to permit movement of the components. More particularly, the present invention relates to a containment system which restrains movable components during travel, such as in the launch of a satellite, and then releases the components to permit movement.
2. The Prior Art
The deployment of a satellite in space is typically performed after the satellite has been carried to a zero gravity orbit by a rocket booster or other vehicle. The satellite is lifted by the launch vehicle and is deployed into a higher stable orbit by imparting a rotational movement to the satellite as the satellite is released. This rotational movement is typically caused by a spin table connected to the launch vehicle which mechanically rotates and releases the satellite. The satellite or other payload can vary in size and weight.
The successful deployment of payloads such as satellites presents an engineering challenge caused by numerous variables. For example, the system for retaining the payload must survive launch forces which may exceed the force of gravity by a multiple of ten. The temperatures affecting the system range from the ambient temperatures of the launch environment to the subzero temperatures in orbit. In addition, the deployment system must be sufficiently strong to handle these variables and the sheer mass of the payload in the most weight efficient manner, as the weight of the deployment system must be lifted by the launch vehicle.
Existing spin tables have been developed to carry a satellite to the deployment elevation and to release the satellite. A spin table generally comprises a large ring gear rotated by pinion gears connected to two drive motors. The ring gear is connected by a rotating structure to the satellite, and this rotating structure rotates on a bearing engaged with the base structure of the system. Initially, the rotating structure contacts the base structure to prevent relative movement during launch. After the satellite has been raised to the deployment elevation, the rotating structure is displaced from contact with the base structure so that the ring gear and rotating structure can spin the satellite relative to the base structure. This displacement of the rotating structure can be accomplished by an off-load spring, shaped as a large Belleville spring, connected between the ring gear and the rotating structure. When the preloaded tension on the off-load spring is released, this spring displaces the rotating structure from contact with the base structure so that the drive motors can spin the ring gear and attached rotating structure and satellite. After the satellite reaches a selected angular speed, the satellite is release from the rotating structure.
There are several disadvantages to using an off-load spring to separate the rotating structure from the base structure. For example, the manufacturing tolerances and specifications of the large off-load spring are precise, and slight variations from such tolerances can result in failure of the entire system. In addition, the off-load spring is subjected to large temperature variations, and these variations can adversely affect the operation of the system. Although the spin table operates in a zero gravity environment, the spin table is typically tested under gravity. In a test of a payload having a weight of six tons, tremendous forces act against the off-load spring, and these forces complicate testing procedures.
For these reasons, a need exists for an improved system for releasable restraining components. The system should be capable of handling large forces without movement, and should be easily removed for deployment of the components.